I took the bus over from Sarajevo and found Belgrade very easy to navigate. There are two main bus terminals, both within short walking distance of the train station; one is basically connected to the train station, while the other is across the street. I was able to buy a multi-use public transportation ticket for 40 Serb dinars and was told the minimum top up was 240 dinars (around $3 total). The card is valid for 3 months and was told this should be good for around 9 bus/tram rides. There is an electric screen you press the card on to deduct the money once entering the bus/tram. I didn’t see anyone do using the card when exiting, so I didn’t either. Most bus/tram stops had a map with a list of stops (showing which direction its heading and connecting services by stop, which I found extremely useful). The #2 tram that does a loop around many of the major sites around downtown. You will pass the bombed out former Ministry of Defense on this tram route and this will also take you to along the castle area near the riverfront, which is definitely worth a visit. The city is a little big to walk everywhere and with the cost of public transportation so cheap, it’s better to use that. It’s also very easy to get to many different domestic and international destinations from Belgrade; bus service gives you more departure options and is definitely the quicker way to go. While there are no public buses going to Timisoara in Romania, a private service offers door-to-door shuttle service for a reasonable 20 euros (also offer from Belgrade to Budapest for 25 euros).

For the more budget conscious, there is currently a special from Belgrade to Budapest for 15 euro by train. You can get the same deal if visiting Novi Sad, just ask for the "Budapest special" otherwise they will charge you the full fare of over 20 euros to go from Novi Sad to Budapest.